# Standard library header <exception>

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This header is part of the error handling library.

### Types
exception | base class for exceptions thrown by the standard library components (class)
nested_exception (C++11) | a mixin type to capture and store current exceptions (class)
bad_exception | exception thrown when std::current_exception fails to copy the exception object (class)
unexpected_handler (deprecated in C++11)(removed in C++17) | the type of the function called by std::unexpected (typedef)
terminate_handler | the type of the function called by std::terminate (typedef)
exception_ptr (C++11) | shared pointer type for handling exception objects (typedef)
### Functions
unexpected (deprecated in C++11)(removed in C++17) | function called when dynamic exception specification is violated (function)
uncaught_exceptionuncaught_exceptions (removed in C++20*)(C++17) | checks if exception handling is currently in progress (function)
make_exception_ptr (C++11) | creates an std::exception_ptr from an exception object (function template)
current_exception (C++11) | captures the current exception in a std::exception_ptr (function)
rethrow_exception (C++11) | throws the exception from an std::exception_ptr (function)
throw_with_nested (C++11) | throws its argument with std::nested_exception mixed in (function template)
rethrow_if_nested (C++11) | throws the exception from a std::nested_exception (function template)
terminate | function called when exception handling fails (function)
get_terminate (C++11) | obtains the current terminate_handler (function)
set_terminate | changes the function to be called by std::terminate (function)
get_unexpected (deprecated in C++11)(removed in C++17) | obtains the current `unexpected_handler` (function)
set_unexpected (deprecated in C++11)(removed in C++17) | changes the function to be called by std::unexpected (function)

### Synopsis

    namespace std {
      class exception;
      class bad_exception;
      class nested_exception;

      using terminate_handler = void (*)();
      terminate_handler get_terminate() noexcept;
      terminate_handler set_terminate(terminate_handler f) noexcept;
      [[noreturn]] void terminate() noexcept;

      int uncaught_exceptions() noexcept;

      using exception_ptr = /* unspecified */;

      exception_ptr current_exception() noexcept;
      [[noreturn]] void rethrow_exception(exception_ptr p);
      template<class E> exception_ptr make_exception_ptr(E e) noexcept;

      template<class T> [[noreturn]] void throw_with_nested(T&& t);
      template<class E> void rethrow_if_nested(const E& e);
    }

#### Class std::exception

    namespace std {
      class exception {
      public:
        exception() noexcept;
        exception(const exception&) noexcept;
        exception& operator=(const exception&) noexcept;
        virtual ~exception();
        virtual const char* what() const noexcept;
      };
    }

#### Class std::bad_exception

    namespace std {
      class bad_exception : public exception {
      public:
        // see [exception] for the specification of the special member functions
        const char* what() const noexcept override;
      };
    }

#### Class std::nested_exception

    namespace std {
      class nested_exception {
      public:
        nested_exception() noexcept;
        nested_exception(const nested_exception&) noexcept = default;
        nested_exception& operator=(const nested_exception&) noexcept = default;
        virtual ~nested_exception() = default;

        // access functions
        [[noreturn]] void rethrow_nested() const;
        exception_ptr nested_ptr() const noexcept;
      };

      template<class T> [[noreturn]] void throw_with_nested(T&& t);
      template<class E> void rethrow_if_nested(const E& e);
    }

### See also

- Error handling

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